Evaluating the performance of tire derived aggregate (TDA) vs natural aggregate in septic system

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Badila, Cornelia Andreea
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This research evaluated the performance of two materials, tire derived aggregate (TDA) and natural aggregate, in the septic field. A full-scale septic system was constructed in Manitoba to investigate the metal leaching effects of TDA in septic fields. The TDA was selected as an alternative to conventional natural aggregate. TDA is one of the repurposing materials made from scrap tires. At the end of its life, scrap tires became a stockpile in a landfill. These stockpiles serve as breeding grounds for diseases carried by mosquitoes and rodents that pose a risk to human health once ignited. The price of disposal of scrap tires led researchers to study beneficial waste tire reuse. A significant use is the use of TDA is to replacement for rock aggregate in different engineering applications. The type A nominal TDA made from off- the road tires was the aggregate chosen for this research. TDA and natural aggregates were implemented in a two-zone trench-style septic field, receiving wastewater from a two-compartment septic tank of a three-bedroom house. The system’s effluent was monitored in the trenches as well as in the soil below the trenches (vadose) at depths of 1 ft and 3 ft. Results of comparison testing between both aggregates showed that the reductions in COD, phosphorous and ammonia concentrations were achieved in both systems without significant differences between the treatments. Concentrations of Ag, Al, Cu, Fe, and Zn in the vadose were below the National Secondary Drinking Water Regulations (NSDWRs). Mn was the only metal that exceeded the NSDWRs in both treatments at one foot below the trench base. Zn, Mn, Cu, Fe and Cr in soil samples were below or within ranges of uncontaminated soils in Manitoba or worldwide. Results suggest that TDA is a feasible substitute for natural aggregate in the septic field.